1. Field of the Invention
This invention relates to a system for purifying the exhaust gas of a spark ignition type, four stroke internal combustion engine, and more particularly, to a system for supplying secondary air into the exhaust gas passage for counterflow into the intake passage to improve the primary combustion of the engine.
2. Description of the Prior Art
Heretofore, there have been proposed various types of exhaust gas purifying devices for engines, but most of them have an air pump as the means for supplying secondary air into the exhaust gas passage near the exhaust valve. These devices have many disadvantages:
1. They are expensive.
2. They constitute a complicated structure.
3. Through it is not always necessary to supply much secondary air in the high speed operation of the engine, much secondary air may be supplied, since a volume type air pump is normally used.
4. As they are bulky, it is difficult to connect them to the engine.
The present invention contemplates the elimination of the aforementioned disadvantages of the conventional devices or systems and provides a novel and improved system for reducing the injurious components of exhaust gas of a spark ignition type, four stroke, internal combustion engine.
It is, therefore, an object of the invention to provide a system for purifying exhaust gas of a spark ignition type four stroke internal combustion engine which is simply constructed and eliminates the use of an air pump.
It is another object of the present invention to provide a system for purifying the exhaust gas of the engine which is characterized by supplying large volumes of secondary air particularly at low speed and low load operation, where the requirements are high for such secondary air.
It is a further object of the present invention to provide a system for purifying the exhaust gas of an engine which is compact and easily incorporated with existing engines.